It is well known that graffiti has become a common eyesore in many cities. A common solution is to simply paint over the offensive markings. However, often, the underlying graffiti will bleed through the paint, particularly if only one coat of paint is used. Further, on a large surface, repainting the smaller area having the graffiti typically will not match the older paint on the remainder of the surface. Repainting the entire surface is even more expensive and time consuming. Additionally, there is considerable expense involved in cleaning traffic signs, such as stop signs, since the sign must be removed and replaced, and then taken to a shop for cleaning; a labor intensive process.
Graffiti is often difficult to remove with conventional solvents. Even then, conventional paint removers such as organic paint solvents, e.g. turpentine, are volatile and have low flash points and have high evaporation rates which make them difficult to use. Further, many solvents, while removing the graffiti, also damage the underlying paint layer and/or surface. A number of chemical compositions for removing graffiti and dried paint in general have been proposed.
For example, U.S. Pat. No. 5,024,780 describes a cleaner to remove graffiti, paint and other coatings, from a surface. The cleaner comprises N-methyl pyrrolidone; propylene carbonate; hydroxy propyl cellulose thixotropic thickening agent; an ingredient selected from the group consisting of diethylene glycol monoethyl ether acetate, dipropylene glycol monomethyl ether acetate, dipropylene glycol methyl ether, diethylene glycol ethyl ether and isocetyI alcohol; and a surfactant.
A cleaner for removing graffiti including ink, marking pen marks and paint from a variety of substrates or surfaces is mentioned in U.S. Pat. No. 5,346,640, which is a continuation-in-part application of a continuation application which became the '780 patent mentioned above. The base composition for all five embodiments comprises N-methylpyrrolidone, propylene carbonate, isocetyl alcohol, an ingredient selected from the group consisting of dipropylene glycol monomethyl ether acetate and dipropylene glycol methyl ether acetate, a thickening agent and a surfactant. Each species or embodiment varies the range of these ingredients and some embodiments include other ingredients, such as dimethyl sulfoxide, a tertiary amine and mineral oil and lavender oil. Each embodiment is directed to a different type of substrate or surface to maximize the removal of graffiti on a surface without any deleterious effects to that surface.
The compositions of the two patents just mentioned are rather complex in that at least six components are required for each composition. In general, the more ingredients a composition has, the more expensive it is to make, both from the cost of the raw materials and the cost of more involved processing to make it. Moreover, these prior art compositions contain ethers, which may have flammability and/or toxicity concerns. It is desirable for paint remover compositions to have very high flash points, but perhaps did not have so many ingredients.